1. Field of the Invention
This disclosure generally relates to robotic systems and, more particularly, to robotic vision based systems operable to determine object pose (location and orientation) in three dimensional space.
2. Description of the Related Art
It is often necessary or desirable to determine object pose (i.e., position and orientation) for objects in controlling robotic systems. However, some objects do not possess clear, visible and/or readily identifiable geometric features, such as sharp, high contrast edges, contours, holes, etc. For example, car body panels such as roofs and hood panels are typically flat and lack sharp or high contrast features.
While computer aided design (CAD) models of the objects may exist, these models are typically difficult to obtain from original equipment manufacturers (OEMs) due to confidentiality concerns. Thus, end users must independently develop their own models of the objects for use with their robotic systems.
Independently developing models is time consuming and expensive. A priori measurements of the geometry of these objects are typically lengthy operations and require specialized equipment, such as coordinate measurement machines, or complex and expensive secondary scanning devices that require a high level of expertise to operate.
A separate challenge is related to the problem of determining the pose of such objects. Given the sparseness or lack of well-constrained visual features such as holes, corners, and fillets on many objects of interest, as well as the typically large size of such objects, the information from one region of the object is often insufficient to determine the overall pose of the object, at least to a sufficient degree of accuracy/repeatability for the required number of degrees of freedom or constraint. In such situations, it may be highly beneficial to have the ability to seamlessly incorporate surface information from one or more additional regions of the object captured by the same or different sensors from one or more stations. Existing methods may provide some insight into addressing the above-described problems of identifying object pose, for example those described in U.S. Pat. Nos. 5,715,166, 6,549,288, 6,392,744, and 5,461,478, all of which are incorporated herein by reference in their entirety.
However, the above U.S. patents are deficient in at least two major areas. First, a priori modeling information is required for the surface geometry of the target objects which, as explained above, may be difficult and/or expensive to obtain. That is, object pose is not determinable in the absence of an object model or other prior known information. Secondly, there are no practical methods for using a relatively small surface region of the object to determine overall object pose, unless that small surface region has unique features and/or characteristics which allow precise determination of pose. For example, determining the pose of an automobile hood based upon a small region is not practical because the hood is typically a relatively flat and smooth surface with no readily discernible unique features and/or characteristics (in at least a small localized area of the hood).
Accordingly, although there have been advances in the field, there remains a need in the art for increasing efficiency in determining object pose, particularly for objects that do not have readily discernible unique features and/or characteristics in at least a small localized area of the object. The present disclosure addresses these needs and provides further related advantages.